1. Field of the Invention
The present invention relates generally to apparatus and methods for conducting well operations at a particular depth and angular orientation within a borehole and more particularly, to apparatus and methods for permanently marking a depth and angular orientation within the borehole, and still more particularly to a reference number set at a particular depth and orientation in the borehole for conducting a well operation such as a sidetracking operation in a single trip into the well.
2. Description of the Related Art
Well operations are conducted at a known location within the well bore. This location may be relative to a formation, to a previously drilled well bore, or to a previously conducted well operation. For example, it is important to know the depth of a previous well operation. However, measurements from the surface are imprecise. Although it is typical to count the sections of pipe in the pipe string as they are run into the borehole to determine the depth of a well tool mounted on the end of the pipe string, the length of the pipe string may vary due to stretch under its own weight and will also vary with downhole temperatures. This variance is magnified when the pipe string is increased in length, such as several thousand feet. It is not uncommon for the well tool to be off several feet when depth is measured from the surface.
In completions it is known to use a no-go ring in the casing string to set a depth location in a well. A typical no-go ring is a thin shouldered device disposed within the casing string which has an inside diameter approximating the drift diameter of the casing string. No-go rings are used to engage and stop the passage of a well tool being run through the well bore. The annular shoulder of a no-go ring is approximately {fraction (1/16)}th of an inch thick on each side so that it will engage the well tool. Other well tools with a smaller diameter are allowed to pass through the no-go ring.
Many well operations require locating a particular depth and azimuth in the borehole for well operations. One such well operation is the drilling of one or more lateral boreholes. One typical sidetracking operation for drilling a lateral wellbore from a new or existing wellbore includes running a packer or anchor into the wellbore on wireline or on coiled tubing and then setting the packer or anchor within the wellbore. The packer or anchor is set at a known depth in the well by determining the length of the wireline or coiled tubing run into the wellbore. A second run or trip is made into the wellbore to determine the orientation of the packer or anchor. Once this orientation is known, a latch and whipstock are properly oriented and run into the wellbore during a third trip wherein the latch and whipstock are seated on the packer or anchor. One or more mills are then run into the wellbore on a drill string to mill a window in the casing of the wellbore. The whipstock is then retrieved. Subsequent trips into the wellbore may then be made to drill the lateral borehole to install a deflector or other equipment for down hole operations.
Further, in conventional sidetracking operations, although the depth of the packer or anchor used to support the whipstock is known, the orientation of the packer or anchor within the wellbore is not known. Thus, a subsequent trip must be made into the wellbore to determine the orientation of the packer or anchor using an orientation tool. The packer or anchor has a receptacle with an upwardly facing orienting surface which engages and orients the orientation tool stabbed into the packer or anchor. The orientation tool then determines the orientation of the packer or anchor within the wellbore. Once the orientation of the packer or anchor has been established, the orientation of the latch, whipstock and mill to be subsequently disposed in the wellbore is then adjusted at the surface so as to be properly oriented when run into the wellbore. The latch, whipstock and mill are then run into the wellbore and stabbed and latched into the packer or anchor such that the face of the whipstock is properly directed for milling the window and drilling the lateral borehole.
Since the packer or anchor are not oriented prior to their being set, the receptacle having the orienting surface and a mating connector may have an orientation that could lead to the receptacle being damaged during future operations. If the receptacle is damaged too badly, then it will not be possible thereafter to use it for orientation and latching of a subsequent well operation.
It is preferred to avoid numerous trips into the wellbore for the sidetracking operation. A one trip milling system is disclosed in U.S. Pat. Nos. 5,771,972 and 5,894,889. See also, U.S. Pat. No. 4,397,355.
In a sidetracking operation, the packer or anchor serves as a downhole well tool which anchors the whipstock within the cased borehole against the compression, tension, and torque caused by the milling of the window and the drilling of the lateral borehole. The packer and anchor have slips and cones which expand outward to bite into the cased borehole wall to anchor the whipstock. A packer also includes packing elements which are compressed during the setting operation to expand outwardly into engagement with the casing thereby sealing the annulus between the packer and the casing. The packer is used for zone isolation so as to isolate the production below the packer from the lateral borehole.
An anchor without a packing element is typically used where the formation in the primary wellbore and the formation in the lateral wellbore have substantially the same pressure and thus the productions can be commingled since there is no zone pressure differentiation because the lower zone has substantially the same formation pressure as that being drilled for the lateral. In the following description, it should be appreciated that a packer includes the anchoring functions of an anchor.
The packer may be a retrievable packer or a permanent big bore packer. A retrievable packer is retrievable and closes off the wellbore while a permanent big bore packer has an inner mandrel forming a flowbore through the packer allowing access to that portion of the wellbore below the packer. The mandrel of the big bore packer also serves as a seal bore for sealing engagement with a another well tool, such as a whipstock, bridge plug, production tubing, or liner hanger. The retrievable packer includes its own setting mechanism and is more robust than a permanent big bore packer because its components may be sized to include the entire wellbore since the retrievable anchor and packer does not have a bore through it and need not be a thin walled member.
One apparatus and method for determining and setting the proper orientation and depth in a wellbore is described in U.S. Pat. No. 5,871,046. A whipstock anchor is run with the casing string to the desired depth as the well is drilled and the casing string is cemented into the new wellbore. A tool string is run into the wellbore to determine the orientation of the whipstock anchor. A whipstock stinger is oriented and disposed on the whipstock at the surface, and then the assembly is lowered and secured to the whipstock anchor. The whipstock stinger has an orienting lug which engages an orienting groove on the whipstock anchor. The whipstock stinger is thereby oriented on the whipstock anchor to cause the face of the whipstock to be positioned in the desired direction for drilling. The whipstock stinger may be in two parts allowing the upper part to be rotated for orientation in the wellbore. The method and apparatus of U.S. Pat. No. 5,871,046 is limited to new wells and cannot be used in existing wells since the whipstock anchor must be run in with the casing and cannot be inserted into an existing wellbore.
U.S. Pat. No. 5,467,819 describes an apparatus and method which includes securing an anchor in a cased wellbore. The anchor may include a big bore packer. The wall of a big bore packer is roughly the same as that of a liner hanger. The anchor has a tubular body with a bore therethrough and slips for securing the anchor to the casing. The anchor is set by a releasable setting tool. After the anchor is set, the setting tool is retrieved. A survey tool is oriented and mounted on a latch to run a survey and determine the orientation of the anchor. A mill, whipstock, coupling and a latch or mandrel with orientation sleeve connected to the lower end of the whipstock are assembled with the coupling allowing the whipstock to be properly oriented on the orientation sleeve. The assembly is then lowered into the wellbore with a lug on the orientation sleeve engaging an inclined surface on the anchor to orient the assembly within the wellbore. The window is milled and then the lateral is drilled. If it is desirable to drill another lateral borehole, the whipstock may be reoriented at the surface using the coupling and the assembly lowered into the wellbore and re-engaged with the anchor for drilling another lateral borehole.
U.S. Pat. No. 5,592,991 discloses another apparatus and method for installing a whipstock. A permanent big bore packer having an inner seal bore mandrel and a releasable setting tool for the packer allows the setting tool to be retrieved to avoid potential leak paths through the setting mechanism after tubing is later sealingly mounted in the packer. An assembly of the packer, releasable setting tool, whipstock, and one or more mills is lowered into the existing wellbore. The packer may be located above or below the removable setting tool. A survey tool may be run with the assembly for proper orientation of the whipstock. A lug and orienting surface are provided with the packer for orienting a subsequent well tool. The packer is then set and the window in the casing is milled. The whipstock and setting tool are then retrieved together leaving the big bore packer with the seal bore for sealingly receiving a tubing string so that production can be obtained below the packer. One disadvantage of the big bore packer is that its bore size will not allow the subsequent smaller sized casing to be run through its bore.
U.S. Pat. No. 5,592,991 describes the use of a big bore packer as a reference device. However, once the releasable setting tool and whipstock are removed from the big bore packer, the packer no longer has sealing integrity. The big bore packer only seals the wellbore after another assembly is lowered into the well and a stinger is received by the big bore packer to create or establish sealing integrity. The big bore packer does double duty, first it serves as the anchor for the milling operation and then it becomes a permanent packer to perform the completion.
In both the ""891 and ""991 patents, the whipstock assembly must latch into the packer or anchor to anchor the whipstock and withstand the compression, tension, and torque applied during the milling of the window and the drilling of the lateral borehole. Further, the use of a big bore packer requires a packer assembly which can withstand a 5,000 psi pressure differential and thus all of its components must have a minimum 5,000 psi burst and collapse capability.
The big bore packer has the additional disadvantage of having a mandrel extending through it and on which is mounted the cones for activating the slips of the packer. The mandrel is subsequently used as a seal bore which is then used for sealing with a tubing string. This mandrel is not only an additional mechanical part but requires a reduction in the diameter of the bore of the packer.
The present invention overcomes the deficiencies of the prior art.
The well reference apparatus and method of the present invention includes a reference member permanently installed within the borehole at a preferred depth and orientation in the well. The reference member provides a permanent reference for the depth and orientation of all well operations, particularly in a multi-lateral well. The assembly of the present invention includes disposing a landing sub, setting member, and reference member on the end of a pipe string. An orienting tool such as an MWD collar is disposed in the pipe string above the landing sub. This assembly is lowered into the borehole on the pipe string. Once the preferred depth is attained, the MWD collar is activated to determine the orientation of the reference member. If the reference member is not oriented in the preferred direction, the pipe string is rotated to align the reference member in the preferred direction. This process is repeated for further corrective action and to verify the proper orientation of the reference member. Upon achieving the proper orientation of the reference member, the reference member is set within the borehole and the pipe string is disconnected from the reference member and the setting member is retrieved. The pipe string may also include a well tool for performing a drilling operation in the borehole.
The present invention features apparatus and methods that permit multiple sidetracking-related operations to be performed using fewer runs into the wellbore. The reference member is placed in the wellbore during the initial trip into the wellbore, and remains there during subsequent operations. Further, the reference member provides a receptacle for reentry runs into the well.
In another aspect, the invention provides for all of the apparatus used during subsequent sidetracking operations to be commonly oriented using only a single orientation on the reference member.
The well reference apparatus and method may be used in a sidetracking operation and include the reference member disposed on setting member, a packer or anchor, a whipstock, a mill assembly, and an orientation device, such as an MWD collar and bypass valve, disposed above the mill assembly in a pipe string extending to the surface. The entire assembly is lowered into the borehole in one trip into the well. Once the reference member has reached the desired depth, fluid flows through the MWD collar allowing the MWD collar to determine and communicate the orientation of the reference member within the borehole. As previously described, the pipe string may be rotated to adjust the orientation of the reference member until the desired orientation is achieved. Once the orientation is complete, the bypass valve is closed and the setting tool is actuated hydraulically to set the reference member permanently within the casing of the borehole. The anchor or packer is then set. A packer is preferred which sealingly engages the wall of the casing. Once the anchor is set, the mill assembly is released from the whipstock and a window is milled through the casing and into the formation.
In another embodiment of the method, an assembly is provided for drilling another lateral borehole spaced out from an earlier lateral borehole. This assembly includes a locator sub, a string of spacer subs extending from the locator sub to a retrievable packer which supports a whipstock and mill assembly. No orientation member is required since the assembly is oriented on the reference member. The retrievable packer supports the upper end of the assembly within the borehole to prevent the instability of the milling and drilling operations on the whipstock.
It should also be appreciated that the reference member has a through bore permitting the performance of operations in that portion of the borehole below the reference member.
Thus, the present invention comprises a combination of features and advantages which enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.